Random sequence switching system with lockout means



March 1965 c. H. WILLYARD ETAL 3,175,189

RANDOM SEQUENCE SWITCHING SYSTEM WITH LOCKOUT MEANS Filed June 6, 1960 a SE? 2: mm m PEST M N .sfi w W E N H R 5%? H 40% M E SE? n E; J Q9 kbfit Q C mm m w Sag lHT HT Qsm 3V3 ESE, i Eli Q Q Q 9 v N .W%

United States Patent ()fitice 3,175,189 Patented Mar. 23, 1965 3,175,189 RANDGM SEQUENCE SWITCHKNG SYSTEM WITH LGCKGUT MEANS Charles H. Wiilyard, Wheaten, and John W. Fink, Chicago, IlL, assignors to Motorola Inc., Chicago, 111., a

corporation of Illinois Filed June 6, 1966, Ser. No. 34,140 t Claims. (Cl. 340-147) This invention relates generally to remote control systems and particularly to a distribution system for applying signals from a large number of input lines through a smaller number of outputs.

In many remote control systems, especially those utilizing wire lines for carrying signals, a problem is presented where many input lines are required for actuating recording equipment through outputs connected to such input lines. It is desirable to have as few outputs as possible thereby minimizing the complexity of recording equipment and in turn, lowering the cost and space required for such equipment. This is especially true of fire station alarm systems wherein it is customary to have many input lines from a large group of fire call boxes connected to a central fire station. In these systems, many fire call boxes are connected in series to each input line and a plurality of input lines are connected to the central fire station. Only a few of such inputlines at the most would ever be in use at the same time to report a fire. It is not necessary to identify the particular input line over which signals are applied from an actuated call box since the call box will identify its location by its code which may be recorded by a paper and pen recorder responsive to signalling which is initiated at the call box.

Therefore, it is an object of the present invention to provide a random distribution switching system which is simple and yet highly reliable.

Another object of the present invention is to provide a random distribution switching system wherein signals from a plurality of input lines are applied to recording apparatus through a smaller number of outputs without affecting system effectiveness.

Still another object of the present invention is to provide a random distribution switching system which may be used with existing multiple line input equipment with a minimum amount of modification to existing equipment.

A feature of the invention is the provision of a random switching control circuit wherein an electron switch device, such as a semiconductor diode or a gas discharge tube having a sharp voltage breakdown characteristic, is used for switching purposes.

Another feature of the invention is the provision of a circuit in a random distribution switching system including a plurality of branches wherein the voltage drop across a resistor in series with an electron switch device on the output side seizes the output shunted across such resistor, thereby preventing conduction of an electron switch device in other branches connected to the same output.

Still another feature of the present invention is the provision of a switching circuit having an energizing device series connected to a resistance, an electron switch device such as a gas discharge device acting as a switch, and a further resistance shunt connected to an output, with the last resistance preventing attempted seizure of the output while it is in use.

Yet another feature of the invention is the provision of a switching circuit having more input lines than outputs and utilizing a pulse voltage developed by an intermittently energized device such as a relay to cause conduction of one of a plurality of electron switch devices each having different voltage breakdown characteristics, each switch device controlling seizure of an output connected in series with the switch device whereby any unseized output may be used with an energized input line.

A still further feature of the invention is the provision of a switching circuit in a multiple branch input line system, wherein an output is connected to a plurality of switching devices individually connected in parallel to input lines, such switching devices selectively conducting current upon energization of an input line, so that signals from a large number of said input lines are applied to a smaller number of outputs.

In the drawings:

FIG. 1 shows in block diagram form a typical fire alarm system wherein the invention may be usedjand FIG. 2 is a schematic diagram of a system showing three typical input line circuits and the associated switching equipment.

In practicing the invention, there is provided a random distribution switching system which may be used at the central station in a fire alarm system. Such fire alarm systems usually have a plurality of fire call boxes connected in series to each of a plurality of lines which feed into a central fire station where a pen and paper recorder is used to record the location of a fire call box which has been actuated. Such call boxes are usually equipped with a spring driven coding mechanism that applies signals to the input lines which are connected to the central fire station to energize a pulse initiating device such as a relay. The pen and paper recorder is used for recording the pulses, each call box transmitting a distinctive number of pulses which form an identifying code. The present invention is directed to a switching or distribution system for use in the central station recording apparatus. A relay may be connected to each input line and has contacts intermittently closed by signals from a fire call box. A capacitor is connected to the contacts to be charged thereby and a resistor is connected from the ca pacitor to a parallel connected group of electron switch devices, such as neon bulbs or semiconductor diodes having sharp voltage breakdown characteristics and which conduct when a predetermined potential is applied thereto. Each switch device is series connected to an output which is shunted by a resistance. Upon energization of a relay connected to an input line, the capacitor connected to the relay contacts will charge and one of the electron switch devices will conduct. When such conduction occurs the voltage drop across the electron switch device will be negligible and the voltage will drop across the other electron switch devices in the group connected in parallel with the energizing relay. Therefore, no other electron switch device in the group will conduct while one of the electron switch devices is conducting. The voltage on the lower side of the conducting switch device will be raised. In turn the voltage on the lower side of each switch device in the various groups connected in parallel with the conducting switch device will be raised thereby preventing firing of any other electron switch device connected to the particular output which has been seized.

Referring now to the drawings, in FIG. 1 there is shown a typical fire alarm box system. Many branch lines may be connected to a central station and each branch line may contain a plurality of call boxes 10. These call boxes are connected in series through energized lines 12 tothe central fire station 16. Each call box will conduct a signal initiated from a call box which may be more remote from the central station. When a lever or chain in the call box is pulled, a spring driven coding mechanism causes line 12 to which the call box is connected, to be pulsed with a code to indicate the location of the actuated call box. Therefore, it is not necessary to known which incoming line 12 is being used since the coded pulse will be decoded at the central station 16.

In FIG. 2 is shown three relay circuits each connected to a branch line 12a, 12b and 120 shown in FIG. 1. The first circuit will be described and includes relay 2% connected to an incoming line 12a. The relay has contacts 22 for connecting an energizing source to capacitor 26 to charge the same when the cont-acts 22 close. The capacitor 26 is connected through resistor 43 to a plurality of switching devices 31, 32, 33, 3440s which may be gas discharge tubes such as neon bulbs, or semiconductor diodes. The switching devices must have a sharp voltage breakdown characteristic which causes them to conduct when a specific potential is applied. The distribution system includes a section such as just described for each input line.

Assume that a signal is received from the first input line 12a. This causes relay contacts 22 to intermittently close. When contacts 22 close, capacitor 26 is rapidly charged and the minus 48 volts on line 12a appears across switching devices 31, 32, 33, 34 through 100. The minus 48 volts is higher than the breakdown voltage of each of the switching devices 31 through 100, but one of the devices will conduct before any of the others. We may assume that device 33 is the first to conduct. Upon conduction, the voltage across device 33 will drop to about one volt or possible less and the flow of current through resistor 43 will drop the voltage across the nonconducting devices 31, 32, 34 through 1%. In other words, the voltage on all of the devices except 33 will be below the breakdown voltage of each of the non-conducting switching devices. Therefore, only switching device 33 will be in a state of conduction. Also, there will be current flow through resistor 63 which shunts output 33 and the voltage drop across resistor 63 will raise the voltage on lead 73 thereby raising the voltage on lead 83 connected to the lower side of all switching devices 233, 333 and so on which are shunting device 33 on the other branches, and such devices will not conduct.

As long as there is sufficient current through device 33 to maintain it in a state of conduction, no other input branch line may be connected through lead 83 to output 33. In the particular branch line which was activated, the maintaining current will be provided by capacitor 26 during' the pulsing period when relay contacts 22 are open.

After the pulsing of contacts 22 is discontinued, capacitor 26 will discharge and after 2. contain time interval, the maintaining current will drop below the critical value for sustaining conduct-ion of switching device 33 thereby switching it to the off condition. When this occurs, output 33 is available for connection to any other input branch line connected to lead 83 through devices 233, 333 and so on. Any input line may then cause conduction of a device connected to leads 83 and 73 causing seizure of output 33 and the previously described operation is then repeated.

The switching arrangement for utilizing any open output is not limited to pulsed signals but may be used with audio signals also. If an audio signal is used, capacitor 26 may not be necessary if relay contact 22 is slow to operate and stays momentarily in a closed position so that one of the switching devices will conduct and thereby seize an available output.

Thus, the invention provides a switching circuit which may be used with a plurality of input branch lines. The branch lines may actuate an energizing device such as a relay which may be series coupled to a resistance and a bank of switching devices. A capacitor is connected to the relay contacts and each switching device is connected in parallel with a corresponding device in other input branch lines and to an output in shunt with a further resistance. The switching circuit may be used advanitageously in any multiple line signalling system but the switching circuit has special applicability especially to a fire call box alarm system where a plurality of call box input branch lines are connected to a central station where pen and paper recorders are used to indicate the code number of an actuated call box. The switching circuit is simple, inexpensive, and highly reliable. The use of such a switching circuit will allow many input branch lines to be used with a fewer number of outputs thereby decreasing the complexity of recording apparatus used with such outputs. The number of outputs required for a particular system may be determined by the number of input branch lines which may be used simultaneously. In fire alarm systems, for example, if 100 input lines are used, past experience has shown that twelve outputs may be adequate.

We claim:

1. A random switching system including in combination, a plurality of input lines, a plurality of output lines, a plurality of first resistor means, means connecting said first resistor means individually between said output lines and a reference potential with each of said first resistor means connected to a different output line, a plurality of line coupling means each associated with a different input line and coupling said associated input line to all of said output lines, each of said line coupling means including, energizing means having a first terminal, capacitor means, second resistor means and a plurality of electron switch means, means connecting said energizing means of each coupling means to said associated input line, said energizing means providing an energizing potential at said first terminal thereof in response to a signal on said associated input line, means connecting said capacitor means between said first terminal and said reference potential, a common terminal, means connecting one of said plurality of electron switch means between said common terminal and each of said output lines, whereby each of said switch means is coupled to a different output line and is in series with a different one of said first resistor means between said common terminal and said reference potential, means connecting said second resistor means between said first terminal and said common terminal, said electron switch means being constructed so that each conducts upon the application of a different predetermined energizing potential thereto, said capacitor means being charged to said energizing potential in response to a signal on said associated input line and applying the potential thereacross through said second resistor means to said series connected electron switch means and first resistor means, one of said plurality of electron switch means conducting current in response to said energizing potential thereacross before any other of said plurality of electron switch means conducts, said conduction providing current flow through said second resistor means and one of said first resistor means to establish a connection between the output line connected to said conducting electron switch means and said associated input line, the potential drop across said second resistor means preventing conduction of any other of said plurality of electron switch means connected to said second resistor means, and the potential drop across said first resistor means preventing conduction of any other electron switch means connected to said first resistor means.

2. A random switching system including in combination, a plurality of input lines, a plurality of output lines, a plurality of first resistor means, means connecting said first resistor means individually between said output lines and a reference potential with each of said first resistor thereof in response to a signal on said associated input line, a common terminal, means connecting one of said plurality of electron switch means between said common terminal and each of said output lines, whereby each of said switch means is coupled to a different output line and is in series with a different one of said first resistor means between said common terminal and said reference potential, means connecting said second resistor means between said first terminal and said common terminal, said electron switch means being constructed so that each conducts upon the application of a different predetermined energizing potential thereto, said energizing potential being applied from said first terminal through said second resistor means to said series connected electron switch means and first resistor means in response to a signal on said associated input line, one of said plurality of electron switch means conducting current in response to said energizing potential thereacross before any other of said plurality of electron switch means conducts, said conduction providing current flow through said second resistor means and one of said first resistor means to establish a connection between the output line connected to said conducting electron switch means and said associated input line, the potential drop across said second resistor means preventing conduction of any other of said plurality of electron switch means connected to said second resistor means and the potential drop across said first resistor means preventing conduction of any other electron switch means connected to said first resistor means.

3. A random switching system including in combina tion, a plurality of input lines, a plurality of output lines, a plurality of first resistor means, means connecting said first resistor means individually between said output lines and a reference potential with each of said first resistor means connected to a diiferent output line, an energizing potential supply means, a plurality of line coupling means each associated with a different input line and coupling said associated input line to all of said output lines, each of said line coupling means including, relay means having normally open contacts thereon, capacitor means having a first terminal connected to said reference potential and a second terminal, second resistor means and a plurality of electron switch means, means connecting said contacts between said potential supply means and said second terminal, means connecting said relay means of each coupling means to said associated input line, said relay means acting on said contacts to cause them to close in response to a signal on said associated input line to provide an energizing potential at said second terminal, a common terminal, means connecting one of said plurality of electron switch means between said common terminal and each of said output lines, whereby each of said switch means is coupled to a different output line and is in series with a different one of said first resistor means between said common terminal and said reference potential, means connecting said second resistor means between said second terminal and said common terminal, said electron switch means being constructed so that each conducts upon the application of a different predetermined energizing potential thereto, said capacitor means being charged to said energizing potential in response to a signal on said associated input line and applying the potential thereacross through said second resistor means to said series connected electron switch means and first resistor means, one of said plurality of electron switch means conducting current in response to said energizing potential thereacross before any other of said plurality of electron switch means conducts, said conduction providing current flow through said second resistor means and one of said first resistor means to establish a connection between the output line connected to said conducting electron switch means and said associated input line, the potential drop across said second resistor means preventing conduction of any other of said plurality of electron switch means connected to said second resistor means and the potential drop across said first resistor means preventing conduction of any other electron switch means connected to said first resistor means.

4-. A random switching system including in combination, a plurality of input lines, a plurality of output lines, a plurality of first resistor means, means connecting said first resistor means individually between said output lines and a reference potential with each of said first resistor means connected to a different output line, an energizing potential supply means, a plurality of line coupling means each associated with a different input line and coupling said associated input line to all of said output lines, each of said line coupling means including, relay means having normally open contacts thereon, second resistor means having first and second terminals and a plurality of electron switch means, means connecting said contacts between said potential supply means and said second terminal, means connecting said relay means of each coupling means to said associated input line, said relay means acting on said contacts to cause them to close in response to a signal on said associated input line to provide an energizing potential at said second terminal, a common terminal, means connecting one of said plurality of electron switch means between said common terminal and each of said output lines, whereby each of said switch means is coupled to a different output line and is in series with a different one of said first resistor means between said common terminal and said reference potential, means connecting said first terminal to said common terminal, said electron switch means being constructed so that each conducts upon the application of a different predetermined energizing potential thereto, said energizing potential being applied from said second terminal through said second resistor means to said series connected electron switch means and first resistor means in response to a signal on said associated input line, one of said plurality of electron switch means conducting current in response to said energizing potential thereacross before any other of said plurality of electron switch means conducts, said conduction providing current flow through said second resistor means and one of said first resistor means to establish a connection between the output line connected to said conducting electron switch means and said associated input line, the potential drop across said second resistor means preventing conduction of any other of said plurality of electron switch means connected to said second resistor means and the potential drop across said first resistor means preventing conduction of any other electron switch means connected to said first resistor means.

References Cited by the Examiner UNITED STATES PATENTS 2,434,989 1/48 Christian 340* X 2,609,454 9/52 Hecht 17918.7

2,780,674 2/57 Six et a1 17918.6

2,914,747 11/59 Straube 340l47 2,954,508 9/60 Burstow 340-175 X FOREIGN PATENTS 1,145,509 5/57 France.

NEIL C. READ, Primary Examiner. IRVING L. SRAGOW, Examiner. 

1. A RANDON SWITCHING SYSTEM INCLUDING IN COMBINATION, A PLURALITY OF INPUT LINES, A PLURALITY OF OUTPUT LINES, A PLURALITY OF FIRST RESISTOR MEANS, MEANS CONNECTING SAID FIRST RESISTOR MEANS INDIVIDUALLY BETWEEN SAID OUTPUT LINES AND A REFERENCE POTENTIAL WITH EACH OF SAID FIRST RESISTOR MEANS CONNECTED TO A DIFFERENT OUTPUT LINE, A PLURALITY OF LINE COUPLING MEANS EACH ASSOCIATED WITH A DIFFERENT INPUT LINE AND COUPLING SAID ASSOCIATED INPUT LINE TO ALL OF SAID OUTPUT LINES, EACH OF SAID LINE COUPLING MEANS INCLUDING, ENERGIZING MEANS HAVING A FIRST TERMINAL, CAPACITOR MEANS, SECOND RESISTOR MEANS AND A PLURALITY OF ELECTRON SWICTCH MEANS, MEANS CONNECTING SAID ENERGIZING MEANS OF EACH COUPLING MEANS TO SAID ASSOCIATED INPUT LINE, SAID ENERGIZING MEANS PROVIDING AN ENERGIZING POTENTIAL AT SAID FIRST TERMINAL THEREOF IN RESPONSE TO A SIGNAL ON SAID ASSOCIATED INPUT LINE, MEANS CONNECTING SAID CAPACITOR MEANS BETWEEN SAID FIRST TERMINAL AND SAID REFERENCE POTENTIAL, A COMMON TERMINAL, MEANS CONNECTING ONE OF SAID PLURALITY OF ELECTRON SWITCH MEANS BETWEEN SAID COMMON TERMINAL AND EACH OF SAID OUTPUT LINES, WHEREBY EACH OF SAID SWITCH MEANS IS COUPLED TO A DIFFERENT OUTPUT LINE AND IS IN SERIES WITH A DIFFERENT ONE OF SAID FIRST RESISTOR MEANS BETWEEN SAID COMMON TERMINAL AND SAID REFERENCE POTENTIAL, MEANS CONNECTING SAID SECOND RESISTOR MEANS BETWEEN SAID FIRST TERMINAL AND SAID COMMON TERMINAL, SAID ELECTRON SWITCH MEANS BEING CONSTRUCTED SO THAT EACH CONDUCTS UPON THE APPLICATION OF A DIFFERENT PREDETERMINED ENERGIZING POTENTIAL THERETO, SAID CAPACITOR MEANS BEING CHARGED TO SAID ENERGIZING POTENTIAL IN RESPONSE TO A SIGNAL ON SAID ASSOCIATED INPUT LINE AND APPLYING THE POTENTIAL THEREACROSS THROUGH SAID SECOND RESISTOR MEANS TO SAID SERIES CONNECTED ELECTRON SWITCH MEANS AND FIRST RESISTOR MEANS, ONE CONNECTED TO SAID SECOND RESISTOR MEANS, AND THE POTENTIAL DROP ACROSS SAID FIRST RESISTOR MEANS PREVENTING CONDUCTION OF ANY OTHER ELECTRON SWITCH MEANS CONNECTED TO SAID FIRST RESISTOR MEANS. 